Higher-order Structure of Polymers Studied by TerahertzSpectroscopy

Abstract

Terahertz（THz） spectroscopy is a powerful tool that uses the low-frequency vibrational modes to elucidatethe intermolecular interaction and the higher order structure of polymers. THz spectroscopy is suitedfor investigating polymer structures because it is very sensitive to the long range structure of large molecules,which is closely related to their physical properties. However, the band assignment of THz spectra of polymershas not been studied well. The present study aims to explore further information about inter- and intramolecularinteractions of polymer materials by THz spectroscopy with the aid of infrared（IR）, low-frequencyRaman spectroscopy, quantum chemical calculations（QCCs） and natural bond orbital（NBO） calculations. Inaddition, THz imaging makes it possible to explore the higher order structure of a sample without altering ordestroying it. In the present study, we have also investigated the characterization of polymer film by THz imaging.Consequently, THz imaging using the intensity ratio of the two spectral peaks at 47 and 67 cm-1 was ableto evaluate the distribution of crystallinity of PCL films. Therefore, THz spectroscopy was shown to be a goodmethod for easy monitoring of inter- and intramolecular hydrogen bondings in the polymer.